SDSR did not tell the RAF to hand the Merlin to the navy, it stated quite clearly it's RAF SH requirements for Future Force 2020, which included 25 RAF operated Merlin helicopters along with puma 2, and the existing chinook strength, plus 14 extra.
It was FRWS (published prior to SDSR and a labour gvt strategy) that outlined the merlin transfer, along with a new buy of 24 (+2 attrition) chinooks to replace the Merlin. Since FRWS was binned some months ago, then I think that the door has still not closed on this issue.